Findings May Explain Gap in Cancer Survival

By RONI CARYN RABIN

Published: August 4, 2009

Scientists say they have made a discovery that may help explain the racial gap in cancer survival, providing clues to why white patients often outlive blacks even when they have what appear to be the same cancers.

The insights come from research at the University of Maryland into throat cancer and squamous-cell cancers of the head and neck, which have been increasing sharply in recent years, apparently because of the human papillomavirus -- the same sexually transmitted virus that causes cervical cancer and is the target of a vaccine for girls.

The virus can also be spread through oral sex, causing cancer of the throat and tonsils, or oropharyngeal cancer.

The new research builds on earlier work suggesting that throat cancer tumors caused by the virus behave very differently from other throat cancers, and actually respond better to treatment. And the new research suggests that whites are more likely than blacks to have tumors linked to the virus, which may explain the poor outcomes of African-Americans with HPV-negative tumors.

University of Maryland researchers did the study after finding that their white patients with throat cancer were surviving 70 months on average, compared with 25 months for their black patients, even though all were treated at the same hospital.

The racial disparity in survival for oropharyngeal cancers explained most of the gap between blacks and whites for all head and neck cancers, the researchers said.

''We were shocked to see this in our own institution, where more than half of the patients we treat are African-American,'' said Dr. Kevin J. Cullen, director of the Greenebaum Cancer Center at University of Maryland and senior author of the new study, in the September issue of Cancer Prevention Research.

Around the same time, the Maryland researchers were analyzing specimens of head and neck tumors gathered from participants in a treatment trial called the TAX 324 study, to determine how many tumors were linked to HPV.

The results were striking: the TAX 324 patients whose tumors were caused by the virus responded much better to treatment with chemotherapy and radiation. And they were also overwhelmingly white.

While about one-half of the white patients' throat tumors were HPV-positive, only one of the black patients had a tumor caused by the virus, Dr. Cullen said.

''There was no difference in the survival between black and white patients in the TAX 324 trials if you subtracted out the HPV-positive patients,'' he said.

The racial gap has often been explained as a result of late diagnosis among African-Americans, lack of access to care and less aggressive treatment, but experts said that in the case of oropharyngeal cancer, there appeared to be distinct biological differences between the tumors.

This suggests that the racial gap in survival for this particular cancer may trace back to social and cultural differences between blacks and whites, including different sexual practices, experts said.

At a briefing for reporters, leading cancer experts called the new report a landmark paper that would transform the treatment of oropharyngeal cancers and challenge doctors to develop new treatment options for patients with HPV-negative tumors.

Dr. Otis Brawley, medical director of the American Cancer Society, who wrote an editorial accompanying the report, said that changing sexual practices were increasing rates of head and neck cancers, and perhaps others as well.